On Sep 28, 2009, at 1:27 PM, Sean Breheny wrote:

>> Can anyone tell me if it is normal for weight positioning to make  
>> such
>> a difference?

It sounds vaguely like the sort of damage that would be caused by  
physically abusing the weighing pan.  "At one time, repeatability was  
0.15mg, but after a couple years of having students slap their samples  
on the pan and then shipping it across the country, that spec is toast."

(one assumes that some pretty careful mechanical design is needed to  
get measurements that are not dependent on position, and that might  
not survive having the flat plate glued to the concave plate, or  
subsequent attempts to remove the flat plate, or ... whatever.  Maybe  
the spec is a marketing number for the sensor and electronics, and  
never was accurate for the full assembly...)

BillW

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